With advance of science and technology, windows are usually coated with tinted window films, or replaced with polymer-dispersed liquid crystal (PDLC) light-regulation membranes, low-emissivity glass or electrochromic glass, so as to retard excessive sunlight from entering buildings. The abovementioned four technologies respectively have their advantages and disadvantages. The PDLC light-regulation membrane and the electrochromic glass can vary the light transmittance thereof or even completely block light. Therefore, the two technologies can meet the demands of users for modern building windows. However, the PDLC membrane is superior to the electrochromic glass in cost and response speed and thus has higher potential to be massively used in building glass.
A U.S. patent publication No. 20110255035 disclosed a “Light-Regulation Membrane”, which comprises a polymer-dispersed liquid crystal layer, a surface structure layer formed on one side of the polymer-dispersed liquid crystal layer, an adhesion layer formed on another side of the polymer-dispersed liquid crystal layer, which is far away from the surface structure layer, wherein the polymer-dispersed liquid crystal layer includes a liquid crystal layer; two conductive layers respectively founed on two sides of the liquid crystal layer; two first polymer layers respectively formed on two sides of the conductive layers, which are far away from the liquid crystal layers; two pressure-sensitive adhesion layers respectively formed on two sides of the first polymer layers, which are far away from the liquid crystal layers; and two second polymer layers respectively formed on two sides of the pressure-sensitive adhesion layers, which are far away from the liquid crystal layers. The light-regulation membrane can be stuck to transparent glass through the pressure-sensitive adhesion layers. An external electric field can be applied to the light-regulation membrane through the conductive layers for twisting the liquid crystal molecules and controlling light transmittance.
Although the polymer-dispersed liquid crystal layer can regulate the amount of the visible light entering the building, it cannot block infrared light that will increase the indoor temperature. While the user allows a great amount of sunlight to illuminate the indoor space, the indoor temperature will rise simultaneously. Thus, a device, such as an air conditioner, is needed to lower the indoor temperature with additional energy consumed. Therefore, how to acquire sufficient illumination and retard undesired infrared light simultaneously has been a target the manufacturers intend to achieve.